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Biomedical subjects

L F Zhang

Publications and source records attributed to L F Zhang.

At least 73 records · Page 4Linked to original sources
PubMed1997

Serotonergic axonal contacts on identified cat trigeminal motoneurons and their correlation with medullary raphe nucleus stimulation.

The innervation of the trigeminal motor nucleus by serotonergic fibers with cell bodies in the raphe nuclei pallidus and obscurus suggests that activation of this pathway may alter the excitability of trigeminal motoneurons. Thus, we recorded intracellular responses from cat jaw-closing (JC) andjaw-opening (JO) alpha-motoneurons evoked by raphe stimulation and used a combination of intracellular staining of horseradish peroxidase (HRP) and immunohistochemistry at the light and electron microscopic levels to examine the distribution of contacts made by serotonin (5-HT)-immunoreactive boutons on the two motoneurons types. Electrical stimulation applied to the nucleus raphe pallidus-obscurus complex induced a monosynaptic excitatory postsynaptic potential (EPSP) in JC (masseter) alpha-motoneurons and an EPSP with an action potential in JO (mylohyoid) alpha-motoneurons. The EPSP rise-times (time to peak) and half widths were significantly longer in the JC than in the JO motoneurons. The EPSPs were suppressed by systemic administration of methysergide (2 mg/kg). Six JC and seven JO alpha-motoneurons were well stained with HRP. Contacts were seen between 5-HT-immunoreactive boutons and the motoneurons. The JC motoneurons received a significantly larger number of the contacts than did the JO motoneurons. The contacts were distributed widely in the proximal three-fourths of the dendritic tree of JC motoneurons but were distributed on more proximal dendrites in the JO motoneurons. At the electron microscopic level, synaptic contacts made by 5-HT-immunoreactive boutons on motoneurons were identified. The present study demonstrated that JC motoneurons receive stronger 5-HT innervation, and this correlates with the fact that raphe stimulation caused larger EPSPs among these neurons than among JO motoneurons.

Animals↗
PubMed1997

Time course and reversibility of arterial vasoreactivity changes in simulated microgravity rats.

Recent works have shown that postflight orthostatic intolerance involves multiple alterations in physiological function during actual or simulated microgravity. In our previous work, we demonstrated that 14-day tail-suspension resulted in an impaired ability of vascular smooth muscle to develop tension in arteries confined to the hindquarter, which have been suggested as an important factor accounting for the occurrence of orthostatic intolerance. To our knowledge, data on arterial vasoreactivity alterations induced by simulated microgravity longer than two weeks are not found. The aim of the present work was to characterize the time course of alterations in vasoconstrictor properties of hindquarter arteries during tail-suspension up to eight weeks, and to examine whether these alterations are reversible.

Adaptation, Physiological↗
PubMed1997

Change in heart rate dynamics after aerobic training detected by approximate entropy and its association with orthostasis.

Findings from the 1973 Skylab mission and early studies led to the conclusion that high level of aerobic capacity might be detrimental to the orthostatic tolerance of returning astronauts. Numerous studies have addressed the problem with conflicting results, further work is needed to establish the relationship between aerobic capacity and orthostasis. During the last two decades, the technique for heart rate variability (HRV) signal analysis developed and have provided a non-invasive probe to examine quantitatively changes in cardiac autonomic balance. In the past, spectral analysis has been used in these studies. During the early 90's, a new mathematical approach and formula termed approximate entropy(ApEn) has been introduced as quantification of regularity and complexity. More recently, ApEn has been used to quantitate the loss of normal nonlinear heart rate variability in a variety of pathological conditions, aging, as well as bed rest deconditioning. The present study was undertaken to assess the effect aerobic training on orthostatic tolerance and HRV analyzed by both conventional AR spectral and ApEn analysis.

Adult↗
PubMed1997

Plasticity of arterial vasculature during simulated weightlessness and its possible role in the genesis of postflight orthostatic intolerance.

Even after several decades of extensive research, the basic mechanism of postflight cardiovascular dysfunction has not yet been fully elucidated. It is now well recognized that multiple mechanisms might account for the frequent occurrence of significant postflight orthostatic intolerance. It has been found that all tissues adapt their design when exposed to sustained alteration in local activity and/or stress. The most obvious example is the musculo-skeletal system, structure and function of which might be severely affected during microgravity exposure. In an attempt to elucidate whether structure and function of cardiac and vascular smooth muscle might be affected by simulated by microgravity, a serial work was started several years ago. In this paper, we present our more recent findings on plasticity of arterial vasculature and its innervation state during and after simulated microgravity and its time course.

Adaptation, Physiological↗
PubMed1997

[Synthesis of carbonyl chlorides substituted with aromatic dense-ring].

Carbonyl chlorides substituted with aromatic dense-ring are chemically active and their fluorescent quantum yields are usually high and they may be used as fluorescent probes for detection of many compounds. Studies on their synthesis and structure activity relationship are very important in the micro-or supermicro-detection of drugs and toxicants containing hydroxy groups. Therefore, the probes may find wide application in the chemical engineering and pharmaceutical industry. Three new fluorescent probes: Beta-(9-anthracene) acrylonyl chloride, Beta-(9-anthracene) propionyl chloride and Beta-( 1-pyrene ) acrylonyl chloride were synthesized by the reaction between the corresponding acid and thionyl chloride. 1-Prenecarboxaldehyde synthesized by using pyrene and N-formyl-N-methylaniline with phosphorus oxychloride as catalyst, was allowed to react with malonic acid to produce Beta-(1-pyrene) acrylic acid for the last-mentioned acid chloride.

Anthracenes↗
PubMed1997

The evaluation of developmental toxicity of chemicals exposed occupationally using whole embryo culture.

The purpose of this study was to employ the whole embryo culture (WEC) system to evaluate the developmental toxicity of industrial chemicals. Five chemicals including lead, cadmium, vinyl chloride, 1,2-dichloroethan, and carbon disulphide were tested in our laboratory both in vitro and in vivo (except lead). In vitro studies showed that cadmium and lead were teratogenic in the rat; whilst carbon disulphide, 1,2-dichloroethan and vinyl chloride mainly induced embryo growth retardation. The in vitro effects on development of the five industrial chemicals were similar to the effects in vivo. The in vitro effects were studied by three different exposure routes, direct exposure--chemicals added to the culture medium; indirect exposure--serum prepared from treated rats then used as culture medium, and pre-exposure--embryos treated maternally then explanted into control (untreated) culture medium. Comparing these three different exposure routes suggests that the last exposure route is the most effective when using WEC to evaluate developmental toxicity of industrial chemicals. The effects on embryo development of culturing in sera prepared from subjects occupationally exposed to antineoplastic drugs (ADs) was also tested by the WEC system. Embryos were cultured with human serum that was thought to contain ADs or ADs' metabolic materials (serum taken from nurses routinely handling ADs), to evaluate the effects of ADs on embryo development. Embryos (9.5-day) cultured with serum from 11 female nurses who had been handling ADs for 2-17 years in the oncology department all survived, but showed slight growth retardation. Embryos cultured with serum from 30 healthy and unexposed people served as controls and embryo development in their serum was normal.

Animals↗
PubMed1997

[Effects of anti-rhTNF alpha monoclonal antibody on oxygen extraction in endotoxemic rabbits].

The effects of anti-rhTNF alpha monoclonal antibody (McAb) on oxygen extraction in endotoxemia rabbits were observed by decreasing total oxygen delivery (DO2) with progressive hypoxia. The result showed that the DO2-VO2 relationship in anti-rhTNF alpha McAb group, like the control group, could be clearly divided into "independent" and "dependent" segment, while the non-correlated antibody group, like the endotoxemic group, never presented any plateau upon breathing the air. Critical oxygen delivery (DO2C) and pooled oxygen extraction rate (ER) in anti-rhTNF alpha McAb group were respectively 10.18 +/- 3.21 ml/(min.kg) and 0.690, not significantly different from those in the control group (10.18 +/- 1.69 and 0.730). The ER in non-correlated antibody group was 0.408, which was significantly lower than that in anti-rhTNF alpha McAb group (P < 0.05), while the plasma TNF alpha concentration was significantly higher (P < 0.01). It was concluded that the monoclonal antibody of recombinant human tumor necrosis factor could block or even reverse the pathologic process of oxygen extraction deficiency caused by endotoxemia.

Animals↗
PubMed1996

Modulation of myocardial alpha 1- but not beta-adrenoceptors after 90-day tail-suspension.

We have previously demonstrated that prolonged simulated microgravity (tail-suspension) leads to cardiac alterations with increased resting heart rate, myocardial degradation changes and attenuated myocardial contractility. The present study investigated the potential role of adrenoceptor mechanisms underlying them. Changes of myocardial alpha 1-adrenoceptor (alpha 1-AR) and beta 1-adrenoceptor (beta-AR) in 90-day tail-suspended rats was investigated by the method of radioligand binding assay and application of Scatchard's method. The results showed significantly decreased quantity of specific binding of 125I-BE[2-beta-(4-hydroxy-3-[125I]indophenyl)-ethylaminomethyltetralone] to alpha 1-AR present in membrane derived from ventricular myocardium of the suspended animals, despite the affinity of the alpha 1-AR to 125I-Be was unchanged. But neither the quantity nor the affinity of beta-AR binding to 125I-Pindolol was significantly altered. In addition, the spontaneously beating rate of isolated right atria from tail-suspended animals showed little change in sensitivity and reactivity to the stimulations of graded phenylephrine (alpha-agonist, measured in the presence of beta-antagonist propranolol) and isoproterenol (beta-agonist), compared with the control rats. There were also no obvious differences of the effects of the isoproterenol on the contractility of isolated left ventricular papillary muscles between the two groups. Since myocardial alpha 1-AR mediated-effects include production of cardiac hypertrophy and enhancement of myocardial glucose uptake and glycolysis, the down-regulation of the alpha 1-AR may be a contributor to the cardiac cellular accumulation and the myocardial degradation changes as found in our tail-suspended rats. The data from this study also suggest that the myocardial beta-adrenoceptors are not affected by the prolonged tail-suspension.

Adrenergic alpha-Agonists↗
PubMed1996

[Heart rate and blood pressure variability: analytical methods, physiological significance, and its applications].

This paper reviews the literature on the methodological issues relevant to signal processing, computation, and clinical applications of heart rate (HR) and blood pressure (BP) variability. Linear techniques for both single signal and relations between the signals, and clinical role of HRV and BPV analysis are examined. Some recent studies in this field are also mentioned.

Animals↗
PubMed1996

Effect of ONO-1078, a leukotriene antagonist, on capsaicin- and substance P-induced bronchoconstriction and airway microvascular leakage in guinea pigs.

AIM: To study the effect of 4-oxo-8-[p-(4-phenylbutyloxy) benzoylamino]-2-(tetrazol-5-yl)-4H-1-benzopyran hemihydrate (ONO-1078), a specific leukotriene antagonist, on capsaicin (Cap)-sensitive sensory nerve functions in the airways, and clarify the modulating roles of endogenous peptido-leukotrienes. METHODS: Changes in intrapulmonary pressure (IPP), Evans blue extravasation in airways, and contraction of bronchial smooth muscles of guinea pigs induced by Cap, substance P (SP) and leukotriene C4 (LTC4) were observed. RESULTS: Cap (0.05 mg.kg-1, i.v.), SP (1 microgram.kg-1, i.v.) and LTC4 (0.5 microgram.kg-1, i.v.) enhanced IPP, and Evans blue extravasation in bronchi and intrapulmonary airways. ONO-1078 0.03 mg.kg-1, i.v. completely blocked the responses to LTC4, attenuated those to Cap, but had no effect to SP. In isolated bronchial smooth muscles, ONO-1078 (1 mumol.L-1) inhibited the contractile response to Cap, but not to SP. CONCLUSION: ONO-1078 partly inhibits Cap-sensitive sensory nerve actions in airways, but has no direct effect on SP, a sensory neuropeptide.

Animals↗
PubMed1995

[Inhibition of chemically induced microvascular leakage by ONO-1078, a leukotriene antagonist, in rat skin].

This study is to determine whether ONO-1078, a potent leukotriene antagonist, influences chemically induced rat skin microvascular leakage which is considered to be, at least in part, due to stimulation of sensory nerve ending and release of sensory neuropeptides. Evans blue dye was used as a tracer for plasma leakage. Intradermal injections of chemical stimuli, histamine (10 micrograms), capsaicin (10 micrograms) and formalin (0.5 mg), evoked Evans blue dye extravasation in rat skin. Intraperitoneal ONO-1078 dose-dependently inhibited the dye extravasation induced by these stimuli, with ID5v values of 1.98 mg.kg-1 for histamine, 1.78 mg.kg-1 for capsaicin, and 2.23 mg.kg-1 for formalin. In contrast to chlorpheniramine, a H1 receptor antagonist, the inhibitory effect of ONO-1078 was weaker on histamine, but more potent on capsaicin and formalin. The inhibitory effect of dexamethasone was more potent than that of ONO-1078 on these stimuli. On the other hand, ONO-1078 inhibited the dye extravasation induced by leukotriene D4 (0.05 micrograms), but showed no effect on those induced by substance P (0.5 micrograms, a sensory neuropeptide), a larger dose of histamine (100 micrograms), and bradykinin (1 microgram). These results suggest that inhibition of chemically induced skin microvascular leakage by ONO-1078 may be mediated by inhibiting the release of sensory neuropeptides from capsaicin-sensitive sensory fibers.

Animals↗
PubMed1995

Effects of ONO-1078, a leukotriene antagonist, on cardiovascular responses induced by vagal stimulation, capsaicin, and substance P in guinea pigs.

AIM: To determine the role of ONO-1078, 4-oxo-8 -[p-(4-phenylbutyloxy) benzoylamino]- 2-(tetrazol-5-yl) -4H-1-benzopyran hemihydrate, in cardiovascular responses induced by vagal stimulation, capsaicin, and substance P. METHODS: Evans blue extravasation in the atrium and ventricle, and mean arterial pressure (MAP) were observed. RESULTS: Electric stimulation of vagus (ESV, 10 Hz, 5 ms, 2 or 10 V, for 90 s) increased Evans blue extravasation in the hearts of atropine (1 mg.kg-1, i.v.)-pretreated guinea pigs. Capsaicin (0.05 mg.kg-1, i.v.) and substance P (1 microgram.kg-1, i.v.) enhanced the dye extravasation and elicited a drop in MAP. ONO-1078 (0.03 and 0.1 mg.kg-1, i.v.) inhibited ESV-induced response, especially at stimulation of 2 V. ONO-1078 (0.03 mg.kg-1) attenuated capsaicin-induced cardiac microvascular leakage and hypotensive response, but failed to inhibit substance P-induced responses. CONCLUSION: ONO-1078 can modulate the cardiovascular responses in neurogenic inflammation, possibly mediated by inhibiting sensory neuropeptide release.

Animals↗